The present invention relates to the measuring the reflectance of light from a surface, and more specifically the light reflected from an eyeglass lens. Furthermore, the present invention measures the reflectance of a surface in percentage reflection.
It is often useful to measure the reflectance of light from a surface. For example, when coating lenses with anti-reflective materials, the reflectance of a surface needs to be checked to verify that the lens has the proper reflectance characteristics. Several devices have been designed to measure lens reflection and optical density. For example, the Liben U.S. Pat. No. 2,451,501 discloses a specular reflectometer that measures the reflectance of flat and curved surfaces used in searchlights and the like. The Liben devices uses a semi-transparent mirror mounted inside a housing. The light source then transmits the light through a lens and the semi-transparent mirror onto the surface. The light reflects from the surface back to the semi-transparent mirror and onto a photoelectric cell. The transmission of light through the lens and the semi-transparent mirror, and the reflecting of light from the surface and the semi-transparent mirror, will cause the light to be repetitively diffused and absorbed. This diffusion and absorption is a disadvantage of the Liben system.
The Heilman U.S. Pat. No. 4,284,356 discloses a method of comparing the reflectance of opposing surfaces. The Heilman device uses light beams directed to opposing sides of a surface. The reflection of these beams are sensed and compared to determine which side of the surface has a reflective coating.
The known reflectance meters are generally bulky and complicated compared to the present invention. The present invention provides a meter that is easy to use and accurate, and, in fact, it is difficult to obtain inaccurate data with this device. In addition, the unique construction of the present invention provides a compact instrument that is relatively simple to manufacture, requires no elaborate optical alignment, and is easy to calibrate. Because of its compact size and easy operating procedures, the present invention is ideal for use in eye health care facilities by both skilled doctors and eye care assistants.